# Question about graph data

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Doug 2013년 4월 12일
I have a graph with temperature on the y axis against time on the x axis.
I was able to find the maximum point of temperature by using this function:
tmaxinner = max(u(:,1));
time along the bottom axis is given by variable 't'.
I would like to get the time value for when the temperature is at its maximum.
I thought something like this would work but it didnt:
timetaken = (t,max(u(:,1));
please can you help
many thanks

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### 답변 (2개)

Leah 2013년 4월 12일
you just need the location of the maximum value.
[tmaxinner locmax]= max(u(:,1));
timetaken = t(locmax,1);
this would give you the first occurrence to the maximum value
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Image Analyst 2013년 4월 12일
Try this:
% Extract times from the 2D (badly-named) u.
times = u(:, 1); % Times are in the first column (I think).
% Extract temperatures from u.
temperatures = u(:, 2); % Temperatures are in the second column (I think).
% Find the max value of the temperatures
% and return the index of that location
[maxTemp, indexOfMaxTemp] = max(temperatures);
% Now we know the array index where the max temperature occurs.
% Get the time that that temperature happened by
% extracting the value of the times array at that same index
timeAtMaxTemperature = times(indexOfMaxTemp);
I hope the code is so well commented that it's basically self-explanatory. If it's not, just ask.
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Doug 2013년 4월 13일
However the code you gave me unfortunately didn't work.
The code that I am writing is plotting the temperature change through a heat shield tile of a given thickness. The variable u holds the temperature data as it progresses through the tile. Here are the graphs that get plotted for the data u and t.
So this is the data that is produced by my code. t is a matrix given by [0:8:4000]. And u is colums of data in rows to correspond to the time data. The thickness of the material is given by the z axis which cannot be seen on the 2d plot.
What I am trying to find is the time at which the inner surface temperature is maximum which is represented by a blue line on the 2d plot.
Many thanks in advance
Image Analyst 2013년 4월 13일
It was not clear from your original question what u was and where I could get the times and temperatures, so that's what I did. Are you saying that you can't make the simple adaptations to my code to get the times and temperatures from whatever variables you have?

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